Thorp Air Command - T18.net

Hey Scott,

Form your ribs using a rivet gun with the head from a modified plastic mallet. This was in the newsletters long ago and it saves a lot of time and effort. As I recall there's about 40 ribs counting right and left, front and back, and this is really a slick way to do it. Here's a picture of the fun I had with it. With a lot of finesse I ended up forming all around the tips without cutting out the small tip radius. The leading edge was closed off for wet wings. Of course, you already know about annealing when necessary.

Les Krumel
Albuquerque

Thanks Les;
We are gaining the experience you speak of. Gary has a rivet gun tool that holds plastic mallet type ends, but I don't know if he's tried it yet. I used soft and hard plastic hammers, including the chisel tip to good effect. I suppose I'll move to the rivet gun driven bumpers now that I've figured out where and how to hit.
The plan is to anneal the tip ribs for full nose forming, not anneal the main ribs because they don't seem to need it.
Gary uses a technique that I'm picking up: he holds the material down to the form with a bucking bar next to the spot he is striking to prevent creep, and possibly shrink the material a bit. perhaps the gap between the bucking bar and the strike point could be reduced using the air hammer?
Once all the tooling blocks are made, ribs should come off pretty quickly. The first tries turned out surprisingly well, I expect they will eventually approach perfection, knowing Gary's high standards.
We have talked about using the press to push an outside form block over the rib blank & block assembly....

_________________
Scott Emery
EAA Chapter 326
T-18 N18TE

Two secrets. First, the buck requires a stiff plate on top of the aluminum. Just using a bucking bar can allow the material to move. I bolt the plate down in two places.
Second, and most important, use a lead slap to shrink around the curve. I pour two slaps at a time. They are about 3/16 thick, 1.5 inches wide, and about 18 inches long. You will be amazed at what they will do.
Cubes